The invention relates to user interfaces capacitive sensors, and in particular to capacitive sensors having illumination associated with a sensing area of the sensor.
There is an increasing demand for robust and aesthetically pleasing user interfaces for controlling devices. Over recent years capacitive touch-sensitive sensing techniques, for example capacitive sensing techniques, have become well established and accepted in this field. Common examples of devices that may include touch-sensitive control panels are touch-sensitive display screens and touch-sensitive keyboards/keypads, e.g. as used for controlling consumer electronic devices/domestic appliances.
In many cases a designer may wish to provide illumination in association with sensing areas (i.e. the touch sensitive regions) of a sensor. For example, sensing areas may be illuminated to aid a user in identifying them in darkened conditions. Illumination of sensing areas may also be used to convey information, e.g. a sensing area may be illuminated to indicate that a function of an apparatus being controlled that is associated with the sensing areas is currently activated. Illumination may also be used for purely aesthetic reasons.
One known technique for illuminating capacitive sensors is to provide a light source in proximity to the sensing area. For example, one technique uses a capacitive sensor comprising a sensing element in the form of a splayed helical spring with a light emitting diode (LED) mounted on axis with the spring so as to illuminated an overlying cover panel from below. Another known technique is to use transparent conductor electrodes in conjunction with a light source behind the sensor and providing illumination of the sensing region through the sensor itself.
These known arrangements can be effective in providing illumination in the region of a sensor's sensing area, but the light source adds complexity to the overall sensor design. The provision of the light source also takes up additional space in the device, which can be particularly problematic in relatively small devices, such as cellular telephones.
There is therefore a need for simplified schemes for providing illumination of sensing areas in capacitive sensors.